Heated flat glass sheets are conventionally formed on vacuum molds utilizing a vacuum on the order of about 10 inches of water column, in other words about 0.025 atmospheres of vacuum. Such vacuums have previously been generated by gas jet pumps such as disclosed by U.S. Pat. No. 4,222,763 McMaster. Blowers can also be utilized to provide the vacuum that forms the glass sheet. In addition, forming of the glass sheet can be provided by separate chambers that provide different levels of vacuum to different areas of the mold such as disclosed by U.S. Pat. No. 4,877,437 Nitschke.
A recently introduced method for forming heated flat glass sheets utilizes a vacuum impulse generated from a vacuum reservoir as disclosed by U.S. Pat. No. 5,376,158 Shetterly et al. Such vacuum impulse forming utilizes a much greater level of vacuum than previously utilized such as on the order of 0.1 atmospheres of vacuum which is over four times the vacuum conventionally utilized to form glass sheets.